A frequency multiplier is an electronic circuit that generates an output signal whose output frequency is a harmonic of its input frequency. Frequency multipliers generally consist of a nonlinear circuit that distorts the input signal and consequently generates harmonics of the input signal. A subsequent bandpass filter selects the desired harmonic frequency and removes the unwanted fundamental and other harmonics from the output.
Frequency multipliers are often used in frequency synthesizers and communications circuits. It can be more economic to develop a lower frequency signal with lower power and less expensive devices, and then use a frequency multiplier chain to generate an output frequency in the microwave or millimeter wave range.
The millimeter wave (mmWave) frequency range has recently become attractive for many applications, such as wireless communications, automotive based radar and imaging applications, etc. The implementation of low phase noise oscillators at such high frequencies, however, is not trivial. Some high frequency oscillator applications incorporate a frequency multiplier which is an important component in many of these systems.